The present invention relates to a method for development of silver halide photographic photosensitive materials and in particular, to a method for inhibition of occurrence of silver sludges in a developer.
It is well known that developers used for development of silver halide photographic photosensitive materials generally contain a sulfite for increase of storage stability of the developers. Furthermore, there may be used developers such as developers for silver salt diffusion transfer process and combined developing and fixing solutions which contain compounds having a strong dissolving action for silver halides, such as thiosulfates, alkanolamines, and thioethers.
When photosensitive materials are processed with the developers containing compounds having a strong dissolving action for silver halides, such as sulfites and thiosulfates, silver complexes dissolve into the developers in a large amount and are readily reduced to generate silver sludges, which are accumulated in the developers. Especially, when photosensitive materials are processed continuously by automatic processors, the silver sludges not only float in the developer, but also stick to rollers and belts, resulting in stains on the photosensitive materials with the precipitated silver which turn yellow or brown upon reflection of light and which are called silver stains in the form of streaks of rollers.
As inhibitors for formation of silver sludges or contamination of solution, there are known 2-mercapto-1,3,4-thiadiazoles (British Patent No.940,169), 2-mercapto-1,3,4-oxadiazoles or 1-phenyl-5-mercaptotetrazoles (U.S. Pat. No.3,173,789), D,L-6,8-dithiooctanoic acid (U.S. Pat. No.3,318,701), o-mercaptobenzoic acid (British Patent No.1,144,481), aliphatic mercaptocarboxylic acids (U.S. Pat. No.3,628,955), 1-thiazolidine-4-carboxylic acids (J. Photogr. Sci., 13, 233 (1965)), disulfide compounds (Japanese Patent Kokai No.52-36029), 2-benzoxazolethiol and 2-benzimidazolethiol (Photogr. Sci. Eng., 20, 220 (1976)), acetylene glycols (Japanese Patent Kokai No.55-95947), 2-mercaptobenzothiazole-5-sulfonic acid (Japanese Patent Kokai No.56-72441), 2-mercaptobenzimidazole-5-sulfonic acid (Japanese Patent Kokai No.60-258537), etc.
However, when these compounds are used as sludge inhibitors in developers having a dissolving action for silver halides, especially developers containing sulfites in a high concentration (for example, 0.3 mol/l or higher), they suffer from the problems that they lose sludge inhibiting effect due to air oxidation, they must be used in a large amount because of their low sludge inhibiting effect, they have adverse effects on photographic characteristics such as desensitization, decrease in contrast and retardation of development, they are expensive and they are malodorous.
Furthermore, Japanese Patent Kokai No.64-50047 proposes a method for inhibiting formation of silver sludges which comprises allowing a cleaning film characterized by comprising a film support and, provided thereon, a hydrophilic colloid layer containing an organic compound capable of adsorbing silver ion or metallic silver to contact with a developer containing a silver complex dissolved therein due to processing of silver halide photosensitive materials. The feature of the invention is to use an organic compound capable of adsorbing silver ion or metallic silver, and there are problems that synthesis of this organic compound needs many steps or is difficult and the cost for the compound is high.
U.S. Pat. No.5,210,009 discloses a method for the recovery of silver according to which a sheet having on the surface a hydrophilic colloid layer containing physical development nuclei is rolled with keeping a space and a developer is passed through the space. However, the recovery of silver is low and this method is still unsatisfactory.
Moreover, Japanese Patent Kokai No.3-273235 describes a filter medium containing physical development nuclei and Japanese Patent Kokai No.3-273236 describes a cleaning film or paper having a hydrophilic colloid layer containing physical development nuclei. According to these methods, the developer containing silver ion or silver complex is filtered by the filter medium or is allowed to contact with the cleaning film or paper, thus the silver ion or silver complex in the developer is precipitated as metallic silver on the physical development nuclei by physical development and as a result, concentration of the silver ion or silver complex in the developer decreases thereby inhibiting the formation of silver sludges. These methods are free from the problems such as deterioration in photographic characteristics and increase in cost which are caused by using the aforementioned sludge inhibitors and thus, are effective for inhibition of sludges. However, these methods are unsatisfactory in keeping stably a high physical developability in the filter having physical development nuclei and it is demanded to inhibit formation of silver sludges by more efficiently capturing the silver ions in the developer.